Question: When did Severus Snape stop being the headmaster of Hogwarts?
Paraphrase: on what serverus snape stop being the headmaster of hogwarts?
SPARQL (Wikidata): SELECT ?value WHERE { wd:Q176772 p:P39 ?s . ?s ps:P39 wd:Q2473303 . ?s pq:P582 ?value}